As it is known, a method implementing Voice over IP transmits a voice communication over a network designed to support a data communication, usually known as a packet switched network. In a packet switched network a plurality of small units of data, usually known as packets, are routed between a sender electronic device and a receiver electronic device on the basis of a destination address, stored within each packet.
This type of communication between the sender and the receiver electronic device is known as a connectionless communication because each packet may follow a different route on the network before reaching the receiver device. More particularly, the Internet is based on the connectionless communication as described above.
A method implementing Voice over IP transmits the voice communication between the sender and the receiver electronic devices connected to a first and a second access point of a Packet switched network. The Internet, that is a Packet switched network used to transmit data communications may be adapted to support voice communications between two electronic devices, for example, located in different nations all over the world and connected to a first and a second access point of the Internet.
In fact, the data to be sent are previously divided in a plurality of packets by a sender electronic device, they are sent over the network and they are finally received by a receiver electronic device, wherein they are recomposed into the original data communication. More particularly, the method implementing Voice over IP is subject to the packet loss during the data communication, and a consequent bad audio quality of the voice communication may result from a high packet loss ratio of the corresponding data communication. In fact, the quality of a voice communication based on a real time voice communication is strictly linked to the percentage of packet loss and to the transmission delay due to the distance between the sender electronic device and the receiver one.
More particularly, experimental results prove that on the Internet the packet loss ratio is between the 0% and the 20%, with delays between 5 ms and 500 ms. Anyway, when the packet loss rate is over 10% and the delay is over the 150 ms the audio quality received at the destination device is considered unacceptable.
A reduction of the packet loss ratio may be achieved through an encoder that reduces the effect of the packet loss on the received data, reconstructing with higher fidelity the corresponding voice communication. More particularly, a known telephony company developed a method for implementing Voice over IP through a personal computer, at the same time reducing the packet loss ratio. This method comprises an encoder and a decoder intended to be installed on a sender personal computer for encoding a voice communication into a data communication at the sender side and, vice versa, for decoding the data communication into a voice communication at the receiver side. More particularly, the sender personal computer comprises a microphone wherein a first user may speak and a loudspeaker wherefrom the first user may hear the voice, for example, the voice of a second user in voice communication with him.
The second user is provided with a corresponding receiver personal computer comprising an encoder and a decoder for encoding the voice communication into a data communication at the sender side and, vice versa, for decoding the data communication into a voice communication at the receiver side. The receiver personal computer also comprises a respective microphone and loudspeaker.
When the first user speaks, the microphone samples his voice and forwards it to the encoder. The encoder processes the sampled voice and encodes it in a corresponding data communication ready to be sent over the Internet. The receiver personal computer of the second user receives through the Internet the data communication. The decoder installed on the receiver personal computer of the second user may process and decode the data communication into a corresponding voice communication, ready to be heard from the loudspeaker.
Such voice communication is less expensive with respect to a voice communication based on a traditional telephone network, like a circuit switched one, because it has the cost of an Internet connection. In addition, the use of a personal computer is not always possible to make a telephone call, being the personal computer, for example a notebook, not intended to be used as a mobile phone, especially for its size and weight.
At the same time, an access point to a packet switched Ethernet, like the Internet, is required to implement the voice communication according to the method described above, such an access point not being always available. Moreover, the hardware configuration of a personal computer not always includes a microphone and a loudspeaker, and the installation and use of a headphone as a peripheral device connected to the personal computer may not particularly appreciated by a user.
The method for implementing Voice over IP in a packet switched network requires that a personal computer or a notebook, provided with a microphone and a loudspeaker, be connected to an access point of the packet switched network. The use of such a personal computer as a mobile telephone may not always be possible because the access point to the packet switched network is not ubiquitous and the personal computer is not as portable as a mobile phone, especially for its size and weight.